This invention relates generally to electrical metering, and more particularly to a method and apparatus for detecting DC influence in a metering current transformer.
At least some known metering systems are influenced in their metering capability by rectified DC loads that draw current through a meter monitoring the consumption of the load. The DC component of the current passing through the current sensor may not transmit through the current sensor, however the DC component may tend to saturate the core of the current sensor. Saturating the core can cause the meter to under-register the current flow and the revenue associated with the current. Some known meters use current transformers (CTs) that are immune or less susceptible to DC influences, however such CTs are relatively more expensive, are larger and tend to have a large phase shift with temperature changes.